1. Field of the Invention
The present invention relates to state-of-charge (SOC) indicators for batteries, and more specifically to pluggable state-of-charge indicators and methods of use thereof.
2. Description of the Prior Art
It is generally known in the prior art to provide indicators for monitoring the state-of-charge (SOC) of rechargeable batteries, such as lithium ion batteries. SOC indicators often are incorporated into the battery housing itself. Soldiers often carry 27.2-45.4 kg(60-100 lbs) of gear, including equipment (e.g., radios) in their rucksack or attached to their vest that operate on rechargeable batteries. As the rechargeable batteries are often inside a rucksack behind the soldier, it would not be practical to have a SOC indicator on the battery housing because the soldier would have to take the rucksack off, open the rucksack, and then check the SOC of the battery. Additionally, a built-in SOC indicator acts as a load, operating continuously and constantly draining the battery that it is monitoring. This reduces the shelf life of the battery and increases maintenance required to make sure the battery has a charge.
Examples of relevant prior art documents include the following:
U.S. Pat. No. 4,413,221 for method and circuit for determining battery capacity by inventors Benjamin et al., filed Dec. 18, 1980 and issued Nov. 1, 1983, is directed to determining the capacity of a battery while charging the battery by measuring the time it takes the battery voltage to decrease to a selected voltage level during discharging intervals interspersed between charging intervals. The state-of-charge is also determined by measuring the voltage level during a discharge interval while monitoring the duration of the charge cycle. Additionally, faulty cells of the battery are detected by measuring the voltage of the individual cells at the end of a discharging interval during the charging of the battery.
U.S. Pat. No. 4,711,248 for physiological pressure monitor by inventors Steuer et al., filed Dec. 1, 1983 and issued Dec. 8, 1987, is directed to a portable physiological pressure monitoring device adapted for being attached to a body part of a patient in which the compartment pressure is to be continuously monitored. The device includes an alarm for indicating when a predetermined maximum pressure limit is exceeded or when a predetermined minimum pressure is not maintained for a certain period of time. The pressure device also includes a hydrophobic filter which separates a catheter and the sensing components of the pressure device for providing sterile operation. A warning also sounds when a battery falls below a given voltage level. Finally, the pressure monitoring device also includes apparatus for measuring nerve conduction velocity and action potential to facilitate better diagnosis and monitoring of compartment syndrome.
U.S. Pat. No. 4,949,046 for battery state of charge indicator by inventor Seyfang, filed Jun. 21, 1998 and issued Aug. 14, 1990, is directed to a device for indicating changes in the state of charge of a rechargeable battery including a current sensor to sense current flow into and out of the battery and to provide an output indicative of both the magnitude and direction of the current flow, a timer to provide a timing signal, and a computer programmed to compute from the output of the current sensor and the timer, a signal representative of the charge dissipated from or accumulated in the battery over a period of time. Preferably the device includes data storage to store an indication of the state of charge of the battery and the computer is programmed to use the signal to update the stored data to provide an indication of the current state of charge of the battery.
U.S. Pat. No. 5,083,076 for portable battery booster by inventor Scott, filed Nov. 13, 1989 and issued Jan. 21, 1992, is directed to a wheeled cabinet that contains two internal booster batteries. Jumper cables are connectible to the booster batteries by a plug-and-socket connector. With the plug disconnected from the socket, end clamps of the jumper cables are applied across a battery or batteries of a vehicle to be jump started. Display lamps are actuated to indicate whether or not the polarity of the jumper cables as connected to the vehicle battery or batteries is correct and whether or not the connection points are appropriate for the potential (12 volt or 24 volt) which should be applied. When it is determined that the connection of the jumper cables to the vehicle batteries is correct, the plug is inserted into the socket to connect the booster batteries to the vehicle battery or batteries and permit jump-starting of the vehicle.
U.S. Pat. No. 5,477,129 for charge level display method and apparatus for a battery of an electronic device by inventor Myslinski, filed Nov. 22, 1993 and issued Dec. 19, 1995, is directed to a portable computer is positionable between an open condition in which an input device and an output device thereof is exposed to a user of the portable computer, and a closed condition in which the input device and the output device is protectively stowed within the portable computer, and further with the portable computer having an “on” state of operation and an “off” state of operation. The portable computer includes a battery, and a display for indicating charge levels of the battery, wherein the display is visible to the user in the open condition and in the closed condition. The portable computer further includes a mechanism for operating the display when the portable computer is in the “on” state of operation and in the “off” state of operation. Moreover, the display is operated to continuously indicate charge levels during the entire “on” state of operation as well as during the entire “off” state of operation.
U.S. Pat. No. 5,705,929 for battery capacity monitoring system by inventors Caravello et al., filed May 23, 1995 and issued Jan. 6, 1998, is directed to a method of and apparatus for centrally monitoring the capacity of batteries in a battery string includes electrical leads connected to each battery terminal of the battery string. A capacity testing system a) switches between the electrical leads for sequentially selecting the leads associated with the terminals of each battery, b) measures the internal resistance of the battery associated with each selected pair of electrical leads, c) compares the internal resistance of each battery cell to an internal resistance threshold, and d) triggers an alarm when the internal resistance of a battery exceeds the internal resistance threshold. A central monitoring station monitors battery capacity data and alarm signals from various battery strings, schedules battery capacity testing, transmits control commands to each capacity testing system for i) scheduling testing, ii) initializing upload of capacity data, and iii) requesting status information, provides battery capacity data analysis, and uploads information to a network management computer. The system is especially suitable for centrally monitoring the capacity of batteries located remote from the central station, preferably in external telecommunications housings and telecommunications power rooms.
U.S. Pat. No. 5,898,290 for battery pack with capacity and pre-removal indicators by inventors Beard et al., filed Sep. 6, 1996 and issued Apr. 27, 1999, is directed to a battery capacity monitoring system readily indicates the remaining capacity of an uninserted battery pack upon an operator's request. Such request may involve the touching of one or more contacts disposed on the battery pack. The battery pack also includes a display and a communication means for communicating capacity information to the device in which it may be installed. The communication means may also be used to display status when the battery pack is not inserted. When inserted a device, the battery pack and device participate to determine time estimates for remaining battery life based on known device loading characteristics and current battery capacity. An operator viewing such information may more adequately determine the usage value of the current battery charge. Moreover, the battery pack and corresponding device are configured to detect the beginning of the process of removing a battery pack. In response, the device saves operational states and data before losing power. Such stored information may be restored upon insertion of another battery pack into the device, permitting the operator to continue where they left off.
US Publication No. 20040189256 for reusable state of charge indicator by inventor Sink, filed Feb. 12, 2004 and published Sep. 30, 2004, is directed to a system and an apparatus for determining the state of charge of a battery, the battery has a sensing device to measure the battery capacity. A reusable state of charge indicator has a microprocessor compatible with different battery types and pre-programmable to determine state of charge based on value received from the sensing device. The battery and the state of charge indicator are electrically connected using one or more contact for providing voltage drop information from the sensing device to the microprocessor. This state of charge indicator is removably attachable to the battery.
US Publication No. 20060017582 for battery monitor by inventors Lockhart et al., filed Aug. 23, 2005 and published Jan. 26, 2006, is directed to an apparatus and method for monitoring at least one battery condition. An ac signal is applied to a battery. A difference between a signal output from the battery and a threshold determines a battery condition. The determined battery condition is transmitted remotely from the battery location either wirelessly or through a network to controller and/or is visibly displayed at the battery location.
U.S. Pat. No. 8,410,783 for detecting an end of life for a battery using a difference between an unloaded battery voltage and a loaded battery voltage by inventor Staton, filed Sep. 30, 2009 and issued Apr. 2, 2013, is directed to one particular implementation conforming to aspects of the present invention takes the form of a method for detecting the end of life of a battery for an electronic device. The method may include calculating the voltage of the battery in an unloaded state, holding the sampled unloaded battery voltage, measuring a loaded battery voltage, calculating the difference between the unloaded and loaded battery voltages and amplifying the calculated difference. Other implementations may take the form of a circuit to perform one or more of the operations of the above method. The circuit may include a sample and hold section and a differential amplifier to provide the amplified difference to a microcontroller for analysis. The microcontroller may also provide a warning or indication to the device or to a user of the device when the battery nears the end of life.
US Publication No. 20120105009 for systems and methods for determining battery state of charge by inventor Yao, filed Jul. 23, 2009 and published May 3, 2012, is directed to systems and methods for determining a state of charge of a battery are provided. The system includes a power source configured to provide a charging current to a battery. A controller is included and configured to determine a state of charge of the battery based on impedance of a battery during a discharge time period based on an impedance and a state of charge relation-ship of a battery during a charge time period.
US Publication No. 20140218200 for circuit protection apparatus by inventor Chen, filed Feb. 2, 2013 and published Aug. 7, 2014, is directed to a circuit protection apparatus. A peripheral interface includes a first power node and a second power node. The circuit protection apparatus includes an auxiliary power supply circuit, a power converter, a first switch, a second switch, a power switch circuit, a warning circuit, and a controller. When a load is plugged to the peripheral interface, the first switch turns on, and the controller is enabled and outputs a control signal, so as to drive the power converter to output power. When the current between input terminal and output terminal of the power switch circuit is larger than a predetermined current, the controller receives the error flag logical voltage outputted by the power switch circuit, cuts off the current between input terminal and output terminal of the power switch circuit, and stops the operations of the power converter.